First Army was established on 10 August 1918 as a field army when sufficient American military manpower had arrived in France during World War I. As an element of the American Expeditionary Forces (AEF) in the latter stages of World War I it was the first of three field armies established under the AEF. Serving in its ranks were many figures who later played important roles in World War II. First Army was inactivated in April 1919.

As part of an army reorganization and final realization of the 1920 amendment to the National Defense Act of 1916, Army Chief of Staff, General Douglas MacArthur directed the establishment of four field armies that each commanded three corps areas that were geographically located. The field armies were established to provide organizational structure for large military organizations that might be mobilized in time of national need.

First Army was located in the northeast United States and was activated on 11 September 1933 at Fort Jay, Governors Island, New York. Initially activated as a paper army, it was commanded by General Dennis E. Nolan. Until 1942, First Army's commander was always the senior commander of one of its three corps areas. The First Corps Area was headquartered in Boston, Massachusetts, Second Corps Area was headquartered at Fort Jay, Governors Island, in New York, New York, and Third Corps Area was located at Fort Howard (Maryland) near Baltimore, Maryland. Since First Army was only a paper organization in its early days, its staff was the existing staff of the corps areas. The overall mission of the First Army was commanding and training regular army, army reserve and national guard units in the three corps areas.

Nolan, the American Expeditionary Force's (AEF) chief of intelligence during World War I was followed by Major General Fox Conner, First Corps Area commander and another AEF veteran and its Chief of Operations. In the years after World War I, Conner was a crucial mentor in the careers of Dwight Eisenhower and George C. Marshall. Passed over as a candidate for Army Chief of Staff for Douglas MacArthur, Conner retired.

In 1938 First Army came under command of General Hugh A. Drum. Drum, who along with a buildup of the Army in 1939 and through the early 1940s, began to develop First Army into a bona fide field army. It began to establish and develop its own staff and participated in the large scale Army maneuvers in Louisiana and North Carolina between 1939 and 1941. As the United States entered World War II, Drum was assigned command of the newly established Eastern Defense Command, responsible for coastal and domestic defense, which relieved First Army of this responsibility on 24 December 1942. Drum retired in 1943 when he reached mandatory retirement age. General George Grunert, commander of Second Service Command, assumed command of First Army until Headquarters, First Army was activated in Bristol, England in January 1944 under command of General Omar Bradley.

First Army's entry into World War II began in October 1943 as Bradley returned to Washington, D.C. to receive his command and began to assemble a staff and headquarters to prepare for Operation Overlord, the codename assigned to the establishment of a large-scale lodgement on the European Continent following Operation Neptune, which was the invasion of Normandy. The headquarters were activated in January 1944 at Bristol, England.

Upon going ashore on 6 June 1944, D-Day, First Army came under General Bernard Montgomery's 21st Army Group (alongside the British Second Army) which commanded all American ground forces during the invasion. Three American divisions were landed by sea at the western end of the beaches, and two more were landed by air. On Utah Beach, the assault troops made good progress, but Omaha Beach came nearest of all of the five landing areas to disaster. The two American airborne divisions that landed were scattered all over the landscape, and caused considerable confusion among the German soldiers, as well as largely securing their objectives, albeit with units completely mixed up with each other. First Army captured much of the early gains of the Allied forces in Normandy. Once the beachheads were linked together, its troops struck west and isolated the Cotentin Peninsula, and then captured Cherbourg. When the American Mulberry harbour was wrecked by a storm, Cherbourg became even more vital.

After the capture of Cherbourg, First Army struck south. In Operation Cobra, its forces finally managed to break through the German lines. The newly established Third Army was then fed through the gap and raced across France.

With the arrival of more US troops in France, the Army then passed from the control of 21st Army Group to the newly arrived 12th Army Group which commanded the First Army and the newly formed Third Army under Lieutenant General George S. Patton. General Bradley assumed command of the 12th Army Group and Lieutenant General Courtney Hodges was placed in command of the First Army. First Army followed Third Army, the American armies forming the southern part of the encirclement of Germans at the Falaise pocket.

When the Germans attacked during the Battle of the Bulge, First Army found itself on the north side of the salient, and thus isolated from 12th Army Group, its commanding authority. It was, therefore, temporarily transferred, along with Ninth Army, back to 21st Army Group under Montgomery on 20 December.[3] The salient was reduced by early February 1945. Following the Battle of the Bulge, the Rhineland Campaign began, and First Army was transferred back to 12th Army Group. In Operation Lumberjack, First Army closed up to the lower Rhine by 5 March, and the higher parts of the river five days later.

On 7 March, in a stroke of luck, Company A, 27th Armored Infantry Battalion, part of Combat Command B, found the Ludendorff Bridge across the Rhine at Remagen still standing. It quickly captured the bridge and established a secure bridgehead. in the next 15 days, over 25,000 troops and their equipment crossed the river. By 4 April, an enormous pocket had been created by First Army and Ninth Army, which contained the German Army Group B under Field Marshal Model, the last significant combat force in the northwest of Germany. While some elements of First Army concentrated on reducing the Ruhr pocket, others headed further east, creating another pocket containing the German Eleventh Army. First Army reached the Elbe by 18 April. There the advance halted, as that was the agreed demarcation zone between the American and Soviet forces. First Army and Soviet forces met on 25 April.

First Army returned to the United States in late 1945; first to Fort Jackson (South Carolina), then to Fort Bragg, North Carolina, returning to Fort Jay, Governors Island, New York, in the spring of 1946. Twenty years later, in 1966, First Army relocated to Fort Meade, Maryland, and took over the responsibilities of Second Army, which was deactivated. In 1973, First Army's mission changed from training and preparation of active units to Army Reserve units. In a 1993 reorganization, five divisions carried out that training and support mission:

In 1993, Headquarters First Army relocated to Fort Gillem, near Atlanta, Georgia, and became responsible for the training and mobilization of all Army Reserve and National Guard units in the United States and providing assistance to the civilian sector during national emergencies and natural disasters. In the latter role, First Army's contributions during the 2005 Hurricane Katrina disaster was a rare bright spot in leading federal relief efforts in the aftermath of the storm. Its commander, Russel L. Honoré, a Louisiana native, became a nationally recognized figure in his direct, no-nonsense approach to disaster relief which earned First Army a Joint Meritorious Unit Award.

In the 21st century, First Army was subjected to more changes as base closures and force structures were instituted to modernize, economize and change its mission. In 2005, a BRAC decision called for the relocation of First Army headquarters to Rock Island Arsenal, Illinois, in 2011. Its former quarters at Fort Gillem was to transition to a single national location for the mobilization and demobilization of Army National Guard and Reserve units.

In a second change, as part of the 2006 reorganization of the United States Army program, First Army exchanged its civilian assistance mission for the training and support missions for military units in the western United States formerly held by US Fifth Army. Fifth Army then became U.S. Army, North with responsibilities for homeland defense and domestic emergency assistance.

First Army deactivated its training divisions and reactivated them as separate training brigades under two commands. First Army Division East, headquartered at Fort George G. Meade, Maryland, has responsibilities in all states east of the Mississippi River; and First Army Division West assuming Fifth Army's role and relocating from Fort Carson to its new headquarters at Fort Hood, Texas, oversees units in all states west of the Mississippi River.

First United States Army was redesignated as First Army on 3 October 2006.

A gold color metal and enamel device 1¼ inches high overall consisting of a black enamel capital letter "A" bearing three gold stars on the top cross bar and five gold on the center cross bar, in front of and interlaced with a gold fleur-de-lis.

The vertical petal is charged in base with a red enamel arrowhead behind and extending above the letter "A" and the tops of the two outside or flanking petals above the cross bar extending over the vertical legs of the letter "A".

The lower ends of the outside petals curve under and over the lower ends of the vertical legs of the letter "A" and are joined together by a gold arched scroll inscribed "First In Deed" in black enamel letters.

The areas within the letter "A" above the center cross bar are white enamel and the areas below the cross bar are red enamel.

Symbolism:

The basic design was suggested by the authorized shoulder sleeve insignia of the First Army.

The Interlaced fleur-de-lis represent wartime service in France and alludes to the initial organization of the Headquarters Company as the Headquarters Troop, First Army at La Ferte-sous-Jouarre, France 10 August 1918.

The First United States Army was organized on 10 August 1918 in the Regular Army in France as Headquarters and Headquarters Troop, First Army.

Headquarters Troop was reorganized and redesignated in September 1918 as Troop A, Headquarters Battalion, First Army. It saw action in the American Expeditionary Force in the latter stages of World War I and included many figures who were later to become very famous, such as Douglas MacArthur.

Troop A, Headquarters Battalion, First Army was redesignated on 1 March 1919, as Headquarters Troop, First Army, and Headquarters and Headquarters Troop, First Army, demobilized on 20 April 1919 in France.

First Army was Constituted 15 August 1927 in the Regular Army as Headquarters and Headquarters Company, Seventh Army, but was Redesignated 13 October 1927 as Headquarters and Headquarters Company, First Army.

Headquarters, First Army activated 1 October 1933 at Fort Jay, Governors Island, New York. It had the mission of training Army formations at the time, as did all the other field armies.

October 1943, Headquarters First Army relocated from Fort Jay, Governors Island, New York to Bristol, England in anticipation of Normandy invasion.

A separate First Army was Reconstituted on 27 June 1944 in the Regular Army as Headquarters and Headquarters Company, First Army; concurrently consolidated with the original Headquarters and Headquarters Company, First Army. The consolidated unit designated as Headquarters and Headquarters Company, First Army.

In 2006, it was announced that subject to Base Realignment and Closure Act, Fort Gillem will eventually be closed and First Army headquarters relocated to Rock Island Arsenal Illinois.

1 December 2006, First Army reorganizes and reflags its five Reserve Component Training Support Divisions into 16 training brigades and establishes two sub-commands, First Army Division East and First Army Division West. First Army East at Fort Meade, Maryland administers eight brigades east of the Mississippi River and First Army West at Fort Hood, Texas, assumes the training responsibilities with eight brigades formerly held by U.S. Fifth Army. Fifth Army becomes U.S. Army, North, and assumes First Army's domestic assistance duties.

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